An ion implantation process is widely used in the manufacture of integrated circuits for implanting a dopant into a substrate. Nowadays, an ion implanter is widely used to implement the ion implantation process. By the ion implanter, the atoms or molecules to be implanted are transformed into ions, then the ions are accelerated in an electrical field to acquire energy, and finally the high-energy ions are implanted into a near-surface region of a substrate. After the ion implantation process is completed, the physical properties of the substrate are changed.
However, in some operating conditions, the dose of dopant implanted into the substrate is higher than the desired dopant dose. Under this circumstance, the performance of the semiconductor device is unstable and the quality is deteriorated.